The aim of our proposed work are: (1) to examine the fine structure of pigment gallstones using electron scanning for chemical analysis ESCA and energy disposive x-ray analysis (EDTA) and th correlate chemical composition with features identified by scanning electron microscopy. (2) To use quantitative thin layer chromatography to examine the bile acid composition of gallstone centers and peripheries. (3) To compare gallstone composition in the United States, Japan, Bolivia, Mexico and India. (4) To compare composition of common duct and gallbladder stones to identify if unique features characterize stones primarily formed in the common ducts. (5) To determine if stone composition will relate to response to chenodeoxycholic acid administration. (6) To determine if the use of discriminant analysis of multiple clinical and biochemical parameters will identify and separate patients with pigment stones from patients with cholesterol stones.